Javascript文字對象，引用自身

Question

我有這個示例代碼：

var foo = {

    self: this,

    init: function(){

        self.doStuff();
    },

    doStuff: function(){
        alert('doing stuff');   
    }

}

foo.init();

為什么反對“自我”不起作用？

謝謝！

Answer 1

因為在您聲明對象文字時， this不是對對象的引用，而是對調用上下文的引用。

Answer 2

值this是由當前的函數是怎么被調用來確定。 它不引用當前對象。

這將有效：

var foo = {
    init: function(){
        this.doStuff();
    },
    doStuff: function(){
        alert('doing stuff');   
    }
};

foo.init();

因為當你調用foo .init() ， this變成了foo 。

Answer 3

按照Qeuntin的回復，您將使用以下內容來實現您的目標

var foo = {

    self: false,

    init: function(){
        self = this
        self.doStuff();
    },

    doStuff: function(){
        alert('doing stuff');   
    },
}

編輯：因為有人指出，雖然這解決了OP的問題（即它有效）但它並不完全是你應該怎么做的。 所以，這是一個范圍參考。

function A()
{
    //Semi-private / hidden var
    var pVar = "I'm a private, err hidden, variable",
        //fn (technically a var)
        pFn = function(){},
        //empty var, placholder for hidden fn
        privatePlaceholderFn;

    //Instance-time... public fn
   this.instancePublicFn = function()
    {
        console.log("--- instace public ---");
        //Print hidden var to cosole
        console.log(pVar);
        //Call hidden fn
        instancePrivateFn();
        console.log("--->Setting  private from instance public")
        //Set the hidden fn
        setPrivate();
        console.log("--- / instance public ---");
    }
    //Pass fn to private method.
    this.setPrivFromOutside = function(fn)
    {
        setPrivateFromPrivateYetOutside(fn);
    }

    //Set the hidden fn
    this.iPFnPlaceholderSetter = function(fn)
    {
        privatePlaceholderFn = fn;
    }

    //Call the semi-private / hidden fn
    this.callPrivate = function()
    {
       privatePlaceholderFn();
    }
    //A misnomer, proves the scope exists. See "function setPrivate()"
    this.setPrivateFromInstance = function()
    {
        //Prove scope exists
        console.log(privatePlaceholderFn);
        console.log("Private From instance - gets inside scope");

    }
    //Set hidden fn from private method
    function setPrivate()
    {
        privatePlaceholderFn = function()
        {
            //Show scope exists
            console.log(pVar);
        }
    }
    //Set the hidden fn from hidden method
    function setPrivateFromPrivateYetOutside(fn)
    {
        //fn's scope won't resolve to inside
        privatePlaceholderFn = fn;
    }
    //Private / hidden messager
    function instancePrivateFn()
    {
        //Just loggin' something
        console.log("Instance Private method");
    }
}
//Add an object method to the prototype
A.prototype.protoPuFn = function(){
    console.log("---> Private var from object literal method");
    //console.log(pVar)
}

//...
a = new A();

//Add object literal fn
a.objFn = function()
{
    console.log("Object literal defined public fn - Gets outside scope");
    //console.log(pVar);
}
//Set private / hidden placeholder fn
a.iPFnPlaceholderSetter(function()
{
    console.log("Hidden fn, passed through instance public - gets outside scope");
    //console.log(pVar);
});
//Attempt to read hidden var
console.log(a.pVar);
//Call object literal defined fn
a.objFn();
//Call the hidden fn
a.callPrivate();
//Call prototype added fn
a.protoPuFn();
//Call instance added public fn
a.instancePublicFn();
//Call private / hidden method (set
a.callPrivate();
//Same as iPFnPlaceholderSetter except the param is passed to a hidden method, before seting.
a.setPrivFromOutside(function()
{
    console.log("-->Passed from outside, through public then private setters");
    //console.log(pVar)
})
//Call the hidden method
a.callPrivate();
//Set hidden fn from instance public
a.setPrivateFromInstance();
//Call the hidden method.
a.callPrivate();
//Use evi(a)l fn to steal scope.
a.evil("this.meth = function(){console.log(pVar)}");
//Call fn with stolen scope
a.meth();

Answer 4

ES6為對象屬性提供了getter，因此您可以使用它們來引用對象本身並使用其他成員：

var foo = {
     prop1: 1,

     get prop2() { return this.prop1 + 1; }
}

// foo.prop2 = 2;